Two-dimensional coupled radio frequency piezoelectric resonator and preparation method thereof

Abstract

The invention discloses a two-dimensional coupled radio frequency piezoelectric resonator and a preparation method thereof. The radio frequency piezoelectric resonator comprises a piezoelectric layerused for fixing the interdigital electrode, and the piezoelectric layer is fixed on the silicon substrate. An upper electrode and a lower electrode of the interdigital electrode are respectively fixedon the upper side and the lower side of the piezoelectric layer, the interdigital electrode positioned on the continuous piezoelectric layer on the cross section is a resonance unit, and at least oneresonance unit is arranged on the piezoelectric layer. The preparation method comprises the following steps: growing a sacrificial layer on a silicon substrate, or directly taking the upper layer ofthe silicon substrate as the sacrificial layer; plating a lower electrode on the surface of the sacrificial layer; growing a piezoelectric layer on the surface of the lower electrode; aligning a lowerelectrode on the upper surface of the piezoelectric layer and plating an upper electrode; etching the resonant unit; and etching the sacrificial layer at the bottom of the lower electrode to form a cavity between the lower electrode of the piezoelectric layer and the silicon substrate below the lower electrode. Electromechanical coupling coefficient of the two-dimensional coupled radio frequencypiezoelectric resonator is increased to 7%-11%.

Description

technical field [0001] The invention relates to a microelectromechanical system (MEMS) piezoelectric resonator based on aluminum nitride (AlN) material, in particular to an AlN resonator structure capable of maximizing the equivalent electromechanical coupling coefficient and a corresponding process. Background technique [0002] RF filters are one of the most important components in the signal processing front-end of modern communication systems. After the Surface Acoustic Wave device (Surface Acoustic Wave device) was invented, because of its relatively simple manufacturing process, different filtering frequency bands can be realized by adjusting the spacing of the Interdigital Transducer (IDT) on the same film. used widely. But limited by the manufacturing process and cost, its operating frequency is limited below 2.5GHz [1]. Thin Film Bulk Acoustic Resonator (FBAR), which utilizes the piezoelectric coefficient d in the thickness direction of the piezoelectric material ...

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Problems solved by technology

However, the frequency of FBAR is mainly determined by the thickness of the material, and a single coating can only achieve one thickness of deposition, so FBAR cannot manufacture multi-frequency devices, and the center frequency of the filter cannot be adjusted through layout design. Thickness uniformity requirements are very high, and its realization process is relatively complicated

In order to overcome such shortcomings and achieve the purpose of adjusting the frequency by using the lithographic size, the Laterally Vibrating Resonator (LVR) [2], [3] was proposed, which uses the d 31 The piezoelectric coefficient, the advantage of this resonator is that the resonant frequency can be changed by adjusting the width of the interdigital electrodes, but the disadvantage is that its equivalent electromechanical coupling coefficient is small

[0003] Existing microelectromechanical systems (MEMS) aluminum nitride piezoelectric resonators using bulk acoustic waves can only use piezoelectric coefficients in a certain direction, such as transverse (d 31 ) or vertical (d 33 ) piezoelectric coefficient

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